Enzymatic hydrolysis of glycosidic bonds generally takes place via general acid-base catalyses that require two critical residues, a proton donor and a nucleophile. The process is illustrated in FIG. 1. Five- or six membered iminocyclitols carrying hydroxyl groups with specific orientation and a secondary amine have been used to mimic the shape and charge of the transition state of the reaction and have been shown to be potent inhibitors of such enzymes (T. A. Beyer, et al., J. Biol. Chem. 1979, 254, 12531–12541; H. Paulsen, et al., Adv. Carbohydr. Chem. Biochem. 1968, 23, 115–232; A. B. Hughes, et al., J. Nat. Prod. Rep. 1994, 135–162; C.-H. Wong, et al., Angew. Chem., Int. Ed. Engl., 1995, 34, 412–432 and 521–546; B. Ganem, Acc. Chem. Res. 1996, 29, 340–347; S. Picasso, Chimia, 1996, 50, 648–649; L. A. G. M. van den Broek, in Carbohydr. Drug Des. 1997; Eds by Z. J. Witczak, et al., Dekker, New York, pp 1–37 and pp471–493; G. W. Fleet. et al., Tetrahedron Lett. 1985, 26, 3127–3130; Y. T Pan, et al., J. Biol. Chem. 1992, 267, 8313–8318; c) T. D. Heightman, et al. Helvetica Chim. Acta 1995, 78, 514–532; and Y. Ichikawa, et al. J. Am. Chem. Soc. 1998, 120, 3007–3018). One process for synthesizing iminocyclitols is based on aldolase-catalyzed reactions (R. L. Pederson, et al., Tetrahedron Lett. 1988, 29, 4645–4648; T. Ziegler, et al., Angew. Chem. Int. Ed. Engl. 1988, 27, 716–717; C. H. von der Osten, et al., J. Am. Chem. Soc. 1989, 111, 2924–3927; T. Kajimoto, et al., J. Am. Chem. Soc. 1991, 113, 6187–6196; K. K.-C. Liu, et al., J. Org. Chem. 1991, 56, 6280–6289; and Y. F. Wang, et al., Angew. Chem. Int. Ed. Engl. 1994, 33, 1242–1244). Another process for synthesizing iminocyclitols is based on multi-step chemical transformations (S. Hiranuma, et al., Tetrahedron Lett. 1995, 36, 8247–8250; and C.-H. Wong, et al., J. Org. Chem. 1995, 60, 1492–1501). A preferred method for assaying inhibition activity without using radioactive isotopes employs electrospray mass spectrometry and capillary zone electrophoresis (CZE) (S. Takayama, et al., J. Am. Chem. Soc. 1997, 119, 8146–8151; J. Wu, et al., Chem. Biol. 1997, 4, 653–657; Y. Kanie, et al., Anal. Biochem. 1998, 263, 240–245; R., Zeleny, et al., Anal. Biochem. 1997, 256, 96–101; K. B. Lee, et al., Anal. Biochem. 1992, 205, 108–114; and K.-B. Lee, et al., Electrophoresis, 1991, 12, 636–640).
Glycosidases and hexoaminidases catalyze a myriad of clinically important processes. For example, cartilage erosion in arthritic subjects results from the over-catabolism of glycosaminoglycans (GAGs) of proteoglycan (PG)-hyaluronate complex, which fills the most part in cartilage tissue. The process is illustrated in FIG. 8. The cartilage PG consists of a central protein core to which GAG side chains of chondroitin sulfate (CS) and keratan sulfate (KS) are attached together with O-linked and N-linked oligosaccharides. The PGs bind to hyaluronic acid noncovalently. The degradation of GAGs is a very complicated process, involving a multi-enzyme systems and radical reactions. It is known that subjects with arthritis have an abnormal increase of β-N-acetylhexoaminidases activities (O. Kida, J. Jap. Orthop. Ass. 1968, 42(6), 4010; R. W. Stephen, et al., Biochim. Biophys. Acta 1975, 399(1), 101, and J. J. Steinberg, et al., Biochim. Biophys. Acta 1983, 757(1), 47). The higher β-N-acetylhexoaminidases activity amplifies that of hyaluronidase and increases the degradation rate of GAG side chains.
What are needed are iminocyclitols having inhibitory activities against hexoaminidases and glycosidases.